Nocturia is a common source of sleep disturbance in men and can result from many different causes. A patient-generated frequency/volume chart, along with several simple mathematical formulas, is used to classify nocturia according to its principal aetiology. The categories are nocturnal polyuria (NP), reduced voided volumes, 24-h polyuria and a combination of the aforementioned factors. Identification of the precise type of nocturia can help direct treatment in the cause-specific manner. In particular, use of the antidiuretic desmopressin can be of benefit in those with NP and may also be useful as part of a combination treatment approach in nocturia of mixed aetiology.